Dynamic BigQuery Schema using Auto Detection:Error Schema has no fields - google-bigquery

Question

I am trying to mess with the auto detection feature in Bigquery and currently I am encountering issues on updating the schema on my table.
What currently I have done.
I created manually a dataset and table name in Bigquery.
Execute my first bq load command (Works perfectly fine):
bq --location=${LOCATION} load --autodetect --source_format=${FORMAT} ${DATASET}.${TABLE} ${PATH_TO_SOURCE}.
I try to append a new JSON object introduced with new field to update the current schema.
Execute 2nd bq load command:
bq --location=${LOCATION} load --autodetect --schema_update_option=ALLOW_FIELD_ADDITION --source_format=${FORMAT} ${DATASET}.${TABLE} ${PATH_TO_SOURCE}
Throws an error:
Error in query string.
Error processing job. Schema has no fields.
I thought when --autodetect flag is enabled bq load command will not request for schema on your load job. Has anyone already encountered this issue?
First object:
{
"chatSessionId": "123",
"chatRequestId": "1234",
"senderType": "CUSTOMER",
"senderFriendlyName": "Player"
}
Second Object:
{
"chatSessionId": "456",
"chatRequestId": "5678",
"senderType": "CUSTOMER",
"senderFriendlyName": "Player",
"languageCode": "EN"
}

Answer 1

I reproduced your steps but I couldn't reproduce the same error as you can see in the images below:
Loading first JSON
First table's data
Loading second JSON
Second's table data
The only thing I changed in your data was the format: you provided a JSON and I turned it into a NEWLINE DELIMITED JSON (type of JSON that BigQuery expects).
You can find more information about it here.
Please let me know if it clarifies something for you.
I hope it helps.